John hays hammond



J. H. HAMMOND. JR, ET AL v MEANS FOR- AND METHOD OF CHANGING THE INTENSITY 0F SIGNALS IN RADIO DYNAMIC RECEIVING SYSTEMS Original Filed June 27, 1917 Nov. 15, 1927. 1,649,778

' h a 2 J 6 5 BY PRSS V To DETECTO R. m 4 Z I 3 To DETECTOR 9 BY Pass.

%llllf Erie/07 1260721 Uhaflee Patented Nov. 15, 19 27 UNITED STATES PATENT OFFICE.

JOHN HAYS HAMMOND, JR, OF GLOUCESTER, AND EMORY LEON GHAIFEE,- OF BEL- MONT, MASSACHUSETTS; SAID CHAFFEE ASSIGNOR T0 SAID HAMMOND.

MEANS FOR AND METHOD*OF CHANGING THE INTENSITY 0F SIGNALS IN; RADIO DYNAMIC, RECEIVING SYSTEMS.

Application filed June 27, 1917, Serial No. 177,202. Renewed May 31, 19 4.

This, invention relates to means for and. methods of reducing the intensity ofstrong signals produced through or pertaining to radiant energy without reducing theintensity ofweak signals. While the invention particularly relates to signals pertaining to radiant energy, it is not so limited in its application. Nevertheless, we shall herein disclose certain forms of means for carrying outour invention and methods for practicing the same, allot which perftaintoreceiving systems employed in conveying messages or signals through the agency of radiant energy.

'In' order that the principles of the invention may be readily understood, we will disclose certain forms or adaptations of the in vention and the best mode known to us for practicing the same, the characteristics of the means preferably employed being best described in terms of its voltage-current curve.

In the drawings,

Fig. 1 represents diagrammatically the type of curve essential to the proper operation of means utilized in the practice of the I invention;

Fig. 2 represents diagrammatically a radio-dynamic receiving system having a. by pass connected across the inductanceofthe antennain accordance with our invention;

3 is a similar diagram but representing the by-pass as connected across the secondary inductance of the system;

Fig. 4 represents the by-pass as connected across the stoppage condenser of the system;

Fig. 5 is adiagram representing one form of by-pass device employed in the practice nals therein, By the accomplishment of such purpose the interference inthe reception of weak signals, due to nearby, powerful transmitting stations or to atmospheric disturbancesknown as static cancbe greatly reduced. Y I In accordance with the preferred embodiment of the invention, means are provided furnishing a leak or by-pass generally'analogous to a resistance, but which is much more effective for" strong vsignals than "for weak signals. Preferably, for this purpose, means are provided having a resistance which decreases as the potential increases. Such meansis effective wherever itbe placed in the receiving system to cut down large peaks of potential Without affecting the small variations of potential, caused by weak signals.

Referring more particularly to the drawings, and first to the diagram designated Fig. 1, I have, therein represented at 1 the type of curve essential or important to the successful operation of the by-pass provided in accordance with the invention. In the diagram the ordinates represent current caused to flow through the leak or by-pass device when voltages represented by the abscissae are impressed across its terminals. .A device having such a curve is characterized by the fact that small diiierences ODE-potential cause very small currents to flow through the device, while large differences of potential cause disproportionately large currents to flow. Such a device is characterized by the fact-that the resistance is a functionof the potential and is very great for small potentials, but is small when large T potentials are impressed across the terminals of the device.

part of a system for receiving radiant energy, providing the part is of such a character that the voltage across its terminals is caused to increase materially by an incoming signal or by static disturbances. In such casethe part across which the 'by-pass is connected will, under predetermined condit'ions, be more or less discharged, the bypassbeing more active for intense signals or disturbances than for weak ones. I

The by-pass employed, one form only of which is disclosed liereimmay be connected in various ways across parts of thelrecei'ving system, and in Figs. 2, 3 and 4 we have represented certain of such ways. It will',how-

Cir

perature coefiicient of resistance.

ever, be understood that the by-pass or other means within the scope and purpose of our invention may be otherwise suitably connected, and that the invention is not limited either to the particular form of means herein disclosed, or to any of the various waysfor connecting said means in receiving systems.

Before describing in detail the form of means herein disclosed for practicing our invention, we will describe certain ways in which such'means or other suitable means may be connected in the receiving system. Any suitable receiving system may be em ployed, that herein represented being merely typical.

In Fig. 2, the primary windingof an oscillation transformer of an open aerial receiving circuit is represented at2. The secondary winding of a closed oscillatory circuit is represented at 3 and a condenser at 4. The by-pass herein employed in the practice of our invention is represented dia grammatically at 5 and is connected by conductors 6 and 7 across the inductance 2.

In F we have represented the'same receiving system having the by-pass device 5 connected byconductors 8 and 9 across the secondary inductance 3.

In Fig. 4:, representing the preferred form of the invention, we have shown the device 5. as connected by conductors l0 and 11 across the stoppage condenser 12, thus pro viding a by-pass in the form of variable leakwhich absolutely prevents the parale ysis of the receiving audion'detector due to excessive charging of the stoppage condenser of the receiving system by intense signals. Such paralysis of the detector is a' well known phenomenon 111 this art, and has been the source of much trouble, which this invention overcomes.

The invention is not limited in its scope to the employment of any particular means for the accomplishment of the object herein stated. Several devices have the essential characteristics shown by the curve of Fig. 1, such for example as crystal contacts and very fine wires, which have a positive temiVhile such devices may be employed by us, we preferably use means of the type shown in Fig. 5.

In said figure, we have shown diagramv matically an electron tube 13, which may be of the general form of that of the well known three-electrode audion detector, but functioning wholly differently. Said tube 13 consists of a highly evacuated member into which is sealed a plate 14:, anelectron emitting filament 15, and a grid 16 situated between the plate and filament. In certain forms of the invention, we may employ a tube or evacuated member having a filament and plate wlthout the grid, bu. by the use 'is impressed between the grid 16 and the negative end of the filament 15, thereby making the grid 16 positive a large flux of electrons passes from the filament 15 to the grid 16. The grid 16 is connected to the circuit 17 containing said battery 17, by a circuit 17 containing the stronger battery 17. If now the plate 1% be connected to the negative end of the filament 15, practically no current will pass in the plate circuit. If, however, the plate 1 1 be made slightly positive in potential with respect to the negative end of the filament 15, a current will pass in the plate circuit, the magnitude depending upon the potential V of Fig. 5, as represented by the curve 1 in Fig.1. A clifference of potential between the plate 14 and the filament 15 of only a volt or so will cause several milliamperes to flow in the plate circuit. The advantage of a high difference of potential between the grid and the filament is illustrated by the family of curves 18 in Fig. 6, each member of which is a plate-voltage, plate current curve fol a certain constant voltage impressed between the grid and the filament. The figures upon the curves in Fig. 6 indicating the number of volts give a rough idea merely of the magnitudes involved.

One manner of connecting the device of Fig. 5 to the receiving circuit in accordance with the preferred method of practicing our invention is represented more in detail in Fig. 7, whereinsuch device is shown con nccted across the stoppage condenser thereof.

In said F 7, the ordinary audion of the receiving circuit is represented at 19, it bcing preferably connected in the usual manner through the stoppage condenser 20 to the oscillatory secondary circuit 21, 22, which in turn is coupled to the inductance 23 of the antenna 2 f. A tube of the general form shown in Fig. 5 is represented at 25. It there constitutes a by-pass, the plate 26 thereof being connected by the conductor 27 to the common. terminals of the parts 20, 21, 22. The negative end of the filament 28 is connected to the junction of the stoppage condenser 20 and the grid 29 of the detector 19. The grid 30 of the tube25 is polarized ill scription the a hy-pass device, such as is shown in Figs. andl7, furnishes a leak analogous to a resistance, that is much'moi e effective for strong signals than for weak signals. A small potential causes a very small current to flow, whereas by doubling the potential the current is increased a great many times, for example, ten or fifteen times. This means that the equivalent resistance in the first case is very high, perhaps several hundredthousand ohms, whereas if the potential becomes two or three times as great, the "effective resistance drops to one or two thousand ohms.

l The invention herein disclosed is characterized by the phenomenon that a resistance which decreasesas the potential increases is effective, substantially wherever it is placed in the receiving system, to cut down large peaks of potential without affecting the small variations of potential caused by weak signals. lvhile themeans is effective Wherever placed in the receiving system, it is peculiarly effective when placed as shown in Figs. t and 7. It then serves double purpose since it not only cuts down the inten sity of the strong signals, but it furnishes the much desired leak on the stoppage condenser necessary for the successful operation of any system using a stoppage condenser.

It will be evident-from the foregoing description that the disclosed by-pass is connected across inductances, condensers, or other parts of a receiving system to reduce large potentials produced atthe terminals of such parts by interference,such latter potentials being in excess of the potentials pro duced by the signals.

Having thus described one illustrative embodiment of our invention and the best method known to us for practicing the same, we desire it to be understood thatalthough specific terms are cmployed, they are used in a generic and descriptive sense and not for purposes of limitatiomthe scope of the invention being set forth in the following claims. j

\Ve clain1- I i I j LA receivingsystem for radio-dynamic energy including aldetector provided with a grid, a stoppage condenseigmeans joining said detector and said condenser, and means for reducing the intensity of strong signals without substantial reduction of the 1ntensity of. Weak signals,said last-mentioned 'nieans comprising a sealed tube having'ciu closedtherein a plate,a filament and a grid, sari d filament'be'mg connected to the junction of said stoppage 'condenser and the'grid of said detector. 7 7

A receivingsystem for radio-dynamic energy including a detector provided with a grid, a stoppage condenser, means joining sa d detector andsaid condenser, and means for reducing the intensity of strong signals 'withont substantial reduction of the intensity of weak signals, said lastanentioned means comprising a sealed tube hav1ngenclosed therein a plate, a" filament and a grid and abattery connected to said last-men .tioned grid and the negative end of'said and abattery connected to said grid, said filament having connected thereto a circuit including chokecoils," and the negative end of said filament beingv connected to the junction of said stoppage" condenser and said first-mentioned grid; 4:. A receiving system for radio-dynamic energy having a stoppage condenser and a by-passtherefor, comprising a sealed tube having therein a plate, a filament and a grid, ,means for heating said filament, and means including a battery connecting said grid to the circuit of said filament. "5. A receiving system for electrical impulses'including a condenser connected in series with respect to a portion of said receiving system carrying the received impulses, and a by-pass therefor, comprising a container having therein a plate, a filament and a grid, said plate being directly connected'to one side of said condenser, said filamentbeing directly connected to the other side of said condenser, and said grid'having a predetermined difference of potential with respect to the filament impressed thereon to determine the functioning voltage of the by.-

pass. I V

6.,Areceiving system for electrical impulses including an oscillatory element connected in series with'respect to a portionof said receiving system carrying the received impulses, and a lay-pass for said'oscillatory element including a container, and a terminal, heating'means, and potential gradient changing means arranged in said container, saidte'rminal being directly connected to one side of said oscillatory element, said lid heating means being connected with the other side of said element,and said potential gradientchanging means having a predetermined diiference of potential impressed thereon with respect to one of the other pants arranged in said container to determine the functioning voltage of the. by-pass.

7 A receiving system for electrical impulses having a detector, a circuit arranged to control said detector and including a oscillatory element, and a by-pass around said oscillatory element. arranged to protect said detector from excessive potentials, said by-pass including a container, and a terminal, electron-discharge means, and potential, gradient changing means arranged in said container, said terminal and said potential, gradient changing means being connected to opposite sides of said oscillatory element respectively.

8. A receiving system for electrical impulses, having a detector, a circuit arranged to control said detector and including a condenser, and a by-pass around said condenser arranged to protect said detector from excessive potentials, said by-pass including a, container, and a terminal, electron-discharge means, andpotential gradient chang: ing means arranged insaid contain-er, said terminal and said potential gradient changing means being connected to opposite sides of said condenser respectively.

9. A receiving system for electrical impulses including a condenser and a bypass therefor, comprising a container having therein a plate, a filament and a. grid, said by-pass being provided with means arranged to heatsaid filament and to maintain said grid at a substantially constant potential with respect to said filament when in opera tion, said plate being connected to one side of said condenser and said filament being connected to the other side of said condenser.

10. A receiving system for electrical impulses including a condenser and a by-pass therefor comprising a container having therein a plate, a filament and a grid, said by-pass being provided with a battery arranged to heat said filament and a battery.

arranged in a circuit connecting said filament and said grid for maintaining said grid at a substantially constant, positive poten tial with respect to said filament when in operation, and said plate and filament being connected respectively with the terminals aic CQHdBSI- 1. A ing system or electri al 1 1,- pulses including an oscillatory element and a by-pass shunted around said oscillatory element in series with respect to a-portion of said e ir gi yst m carry n h eceived i p es nd inslildi i a con i e provided with an anode, a cathode, and a grid, said anodebeing c nnect-ed to. one side "o said; o eill e y element sa d. ara esing connected to the other side of said oscillatory element, and said grid having a pie determined difference of potential impressed thereon with respect to one of the other parts provided in the container to determine the functioning voltage of the by-pass.

12. A receiving system for electrical impulses including an oscillatory element and a by-pass shunted around said oscillatory element and including a container provided with an anode, a cathode, and a potential gradient changing means, said anode being connected to one side of said oscillatory element, said cathode being connected to the other side of said oscillatory element, and said potential gradient changing means being so connected with the cathode as to be held at a substantially constant potential with respect to said cathode while in operation.

13. A receiving system for radiant energy comprising a detector having input and output circuits, a source of energy on the input side of the detector in the form of a transformer having its secondary winding connected with the detector, an impedance element connected in series between said winding and the detector and across which potentials may be induced, and means independent of the output circuit for providing a resistance in shunt with said element which is much less for differences of potentialabove a predetermined value than for smaller differences of potential. Y

14. A receiving system for radiant energy comprisingv a detector having input and out put circuits, a closed, oscillatory circuit responsive to electrical oscillations and peratively connected with the input side of the detector, an impedance element connected in series between the oscillatory circuit and the detector and across which potentials may be induced, and means independent of the output circuit for providing a resistance in shunt with said element which is much less for differences of potential above a predetermined value than for smaller differences of potential.

15. A receiving system for radiant energy comprising a detector, a closed, oscillatory circuit responsive to electrical oscillations and operatively connected with the input side of the detector, a condenser connected in series between the closed. oscillatory circuit nected with the input side of the detector, an impedance element connected in series between the oscillatory circuit and the grid of the detector and across which high potentials may be induced, and a thermionic tube connected in shunt with said impedance element and acting to oppose less resistance to the passage of currents at high potentials than at low potentials.

17. A receiving system for radiant energy comprising a detector, a closed, oscillatory circuit responsive to electrical oscillations and operatively connected with the input side of the detector, an impedance element 1 connected in series between the oscillatory duced, a three-electrode, thermionic tube having itsplate and filament connected respectively to the terminals of said element, a source of potential interposed between the grid and filament of said tube for determining the voltages for which the tube will serve as a by-pass for said impedance element, and means for confining the variations of potential of the impedance element to the filament and preventing such variations from affecting the grid.

19. A receivingsystem for radiant energy comprising an impedance element across the terminals of which potentials may be induced, a three-electrode, thermionic tube having its plate and filament connected respectively to the terminals of said element, a heating circuit for the filament, a source of positive potential with respect to the grid interposed between the grid and filament of said tube fordetermining the voltages for which the tube will serve as a bypass for said impedance element, and means for con fining the variations of potential of the impedance element to the filament, said means including a choke coil connected in the heating ci' "cuit of the filament.

20. A receiving system for radiant energy comprising an impedance element across the terminals of which potentials may be induced, a three-electrode, thermionic 7 tube having its plate and filament connected respectively to the terminals of said element and its grid connected with its filament, and means for confining the variations of poten tial of the impedance element to the filament and preventing such variations from affecting the grid.

In testimony whereof, We have signed our names to this specification.

JOHN HAYS HAMMOND, JR. EMORY LEON CHAFFEE. 

